feat: unified shell, diagnostics pack, native Office, sticky board

Make Surface remote debugging and classroom workflows viable: always-on
structured logs with one-click zip export, a single AppShell chrome,
OOXML PPTX/DOCX annotation without LibreOffice, and a first-class sticky
board. Also drop spike/legacy ink widgets and tighten pen feel
(predictor, PenInfoHistory, page-tile layer).

Co-authored-by: Cursor <cursoragent@cursor.com>

lib/main.dart

@@ -2,15 +2,15 @@ import 'package:dynamic_color/dynamic_color.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter_localizations/flutter_localizations.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
-import 'package:google_fonts/google_fonts.dart';
 import 'package:pdfrx/pdfrx.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 
 import 'editor/persistence/sidecar_flush_observer.dart';
-import 'editor/pdf/pen_capture_region.dart';
+import 'theme/app_theme.dart';
+import 'diagnostics/badnote_log.dart';
 import 'l10n/app_localizations.dart';
 import 'providers/settings_provider.dart';
-import 'screens/home_screen.dart';
+import 'screens/app_shell.dart';
 import 'screens/vault_setup_screen.dart';
 import 'services/database_service.dart';
 import 'services/vault_service.dart';
@@ -18,11 +18,7 @@ import 'services/webdav_sync_service.dart';
 import 'storage/sqlite_to_sidecar_migrator.dart';
 
 Future<void> main() async {
-  // Kind-aware binding (extends WidgetsFlutterBinding) must be the active
-  // binding before runApp so the M1 spike's PenCaptureRegion can gate
-  // hit-testing by pointer kind. Safe for the rest of the app: with no pen
-  // region mounted it behaves exactly like the default binding.
-  PenCaptureBinding.ensureInitialized();
+  WidgetsFlutterBinding.ensureInitialized();
   // pdfrx native engine init (required before any PdfViewer is built).
   pdfrxFlutterInitialize();
 
@@ -32,6 +28,10 @@ Future<void> main() async {
   // Initialize SharedPreferences
   await SharedPreferences.getInstance();
 
+  // Always-on structured diagnostics (Surface remote debugging).
+  await BadNoteLog.instance.start();
+  BadNoteLog.instance.info(LogSubsystem.shell, 'app_start');
+
   runApp(const ProviderScope(child: BadNoteApp()));
 }
 
@@ -81,8 +81,8 @@ class _BadNoteAppState extends ConsumerState<BadNoteApp> {
         return MaterialApp(
           title: 'BadNote',
           themeMode: settings.themeMode,
-          theme: _theme(lightScheme),
-          darkTheme: _theme(darkScheme),
+          theme: AppTheme.fromScheme(lightScheme),
+          darkTheme: AppTheme.fromScheme(darkScheme),
           // i18n: follows the OS language (en / zh) via the system locale.
           localizationsDelegates: const [
             AppLocalizations.delegate,
@@ -96,14 +96,6 @@ class _BadNoteAppState extends ConsumerState<BadNoteApp> {
       },
     );
   }
-
-  ThemeData _theme(ColorScheme scheme) => ThemeData(
-        colorScheme: scheme,
-        useMaterial3: true,
-        textTheme: GoogleFonts.interTextTheme(
-          ThemeData(brightness: scheme.brightness).textTheme,
-        ),
-      );
 }
 
 /// Startup gate: shows [HomeScreen] only once a valid vault root folder has been
@@ -213,7 +205,7 @@ class _VaultGateState extends State<VaultGate> {
         ),
       );
     }
-    if (_valid) return const HomeScreen();
+    if (_valid) return const AppShell();
     return VaultSetupScreen(
       vaultService: _vault!,
       missing: _hadStoredPath,